Catalytic upgrading of crude tire oil produced from hydrothermal liquefaction of scrap tire using Pd/Al2O3 nanocomposite

In this study, hydrothermal catalytic upgrading of crude tire oil was conducted in the presence of formic acid to decrease the viscosity, increase the high heating value (HHV), and improve the chemical composition of the liquid crude tire oil. Palladium nanoparticles immobilized on the surface of magnetic alumina (Pd/Al2O3/Fe3O4) were used as the catalyst. The catalyst had surface area of 101.67 m2/g and micropore volume of 0.31 cm3/g. Furthermore, EDS analysis showed that the palladium content of the catalyst was 2.29 wt%. Crude tire oil was produced by using the hydrothermal liquefaction process of scrap tire oil in presence of deionized water with a tire/water mass ratio of 1:4 in a molten salt bath using a cylindrical batch reactor. The effect of temperature (280-350 degrees C) and reaction time (20-120 min) on the upgrading process was evaluated. Finally, the Central Composite Design (CCD) method was applied for optimizing the process to increase mass and energy yield and improve the quality of the produced fuel. The mass yield of the produced fuel oil was in the range of 61 to 93 %. The results of the catalytic upgrading process illustrated that the content of sulfur and oxygen in the optimum state, compared to the crude tire oil, decreased by 86 % and 53 %, respectively; also, the HHV increased by 11 %.